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Java example source code file (IIOMetadata.java)
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The IIOMetadata.java Java example source code
/*
* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package javax.imageio.metadata;
import org.w3c.dom.Node;
import java.lang.reflect.Method;
/**
* An abstract class to be extended by objects that represent metadata
* (non-image data) associated with images and streams. Plug-ins
* represent metadata using opaque, plug-in specific objects. These
* objects, however, provide the ability to access their internal
* information as a tree of <code>IIOMetadataNode objects that
* support the XML DOM interfaces as well as additional interfaces for
* storing non-textual data and retrieving information about legal
* data values. The format of such trees is plug-in dependent, but
* plug-ins may choose to support a plug-in neutral format described
* below. A single plug-in may support multiple metadata formats,
* whose names maybe determined by calling
* <code>getMetadataFormatNames. The plug-in may also support
* a single special format, referred to as the "native" format, which
* is designed to encode its metadata losslessly. This format will
* typically be designed specifically to work with a specific file
* format, so that images may be loaded and saved in the same format
* with no loss of metadata, but may be less useful for transferring
* metadata between an <code>ImageReader and an
* <code>ImageWriter for different image formats. To convert
* between two native formats as losslessly as the image file formats
* will allow, an <code>ImageTranscoder object must be used.
*
* @see javax.imageio.ImageReader#getImageMetadata
* @see javax.imageio.ImageReader#getStreamMetadata
* @see javax.imageio.ImageReader#readAll
* @see javax.imageio.ImageWriter#getDefaultStreamMetadata
* @see javax.imageio.ImageWriter#getDefaultImageMetadata
* @see javax.imageio.ImageWriter#write
* @see javax.imageio.ImageWriter#convertImageMetadata
* @see javax.imageio.ImageWriter#convertStreamMetadata
* @see javax.imageio.IIOImage
* @see javax.imageio.ImageTranscoder
*
*/
public abstract class IIOMetadata {
/**
* A boolean indicating whether the concrete subclass supports the
* standard metadata format, set via the constructor.
*/
protected boolean standardFormatSupported;
/**
* The name of the native metadata format for this object,
* initialized to <code>null and set via the constructor.
*/
protected String nativeMetadataFormatName = null;
/**
* The name of the class implementing <code>IIOMetadataFormat
* and representing the native metadata format, initialized to
* <code>null and set via the constructor.
*/
protected String nativeMetadataFormatClassName = null;
/**
* An array of names of formats, other than the standard and
* native formats, that are supported by this plug-in,
* initialized to <code>null and set via the constructor.
*/
protected String[] extraMetadataFormatNames = null;
/**
* An array of names of classes implementing <code>IIOMetadataFormat
* and representing the metadata formats, other than the standard and
* native formats, that are supported by this plug-in,
* initialized to <code>null and set via the constructor.
*/
protected String[] extraMetadataFormatClassNames = null;
/**
* An <code>IIOMetadataController that is suggested for use
* as the controller for this <code>IIOMetadata object. It
* may be retrieved via <code>getDefaultController. To
* install the default controller, call
* <code>setController(getDefaultController()). This
* instance variable should be set by subclasses that choose to
* provide their own default controller, usually a GUI, for
* setting parameters.
*
* @see IIOMetadataController
* @see #getDefaultController
*/
protected IIOMetadataController defaultController = null;
/**
* The <code>IIOMetadataController that will be
* used to provide settings for this <code>IIOMetadata
* object when the <code>activateController method
* is called. This value overrides any default controller,
* even when <code>null.
*
* @see IIOMetadataController
* @see #setController(IIOMetadataController)
* @see #hasController()
* @see #activateController()
*/
protected IIOMetadataController controller = null;
/**
* Constructs an empty <code>IIOMetadata object. The
* subclass is responsible for supplying values for all protected
* instance variables that will allow any non-overridden default
* implementations of methods to satisfy their contracts. For example,
* <code>extraMetadataFormatNames should not have length 0.
*/
protected IIOMetadata() {}
/**
* Constructs an <code>IIOMetadata object with the given
* format names and format class names, as well as a boolean
* indicating whether the standard format is supported.
*
* <p> This constructor does not attempt to check the class names
* for validity. Invalid class names may cause exceptions in
* subsequent calls to <code>getMetadataFormat.
*
* @param standardMetadataFormatSupported <code>true if
* this object can return or accept a DOM tree using the standard
* metadata format.
* @param nativeMetadataFormatName the name of the native metadata
* format, as a <code>String, or null if there
* is no native format.
* @param nativeMetadataFormatClassName the name of the class of
* the native metadata format, or <code>null if there is
* no native format.
* @param extraMetadataFormatNames an array of <code>Strings
* indicating additional formats supported by this object, or
* <code>null if there are none.
* @param extraMetadataFormatClassNames an array of <code>Strings
* indicating the class names of any additional formats supported by
* this object, or <code>null if there are none.
*
* @exception IllegalArgumentException if
* <code>extraMetadataFormatNames has length 0.
* @exception IllegalArgumentException if
* <code>extraMetadataFormatNames and
* <code>extraMetadataFormatClassNames are neither both
* <code>null, nor of the same length.
*/
protected IIOMetadata(boolean standardMetadataFormatSupported,
String nativeMetadataFormatName,
String nativeMetadataFormatClassName,
String[] extraMetadataFormatNames,
String[] extraMetadataFormatClassNames) {
this.standardFormatSupported = standardMetadataFormatSupported;
this.nativeMetadataFormatName = nativeMetadataFormatName;
this.nativeMetadataFormatClassName = nativeMetadataFormatClassName;
if (extraMetadataFormatNames != null) {
if (extraMetadataFormatNames.length == 0) {
throw new IllegalArgumentException
("extraMetadataFormatNames.length == 0!");
}
if (extraMetadataFormatClassNames == null) {
throw new IllegalArgumentException
("extraMetadataFormatNames != null && extraMetadataFormatClassNames == null!");
}
if (extraMetadataFormatClassNames.length !=
extraMetadataFormatNames.length) {
throw new IllegalArgumentException
("extraMetadataFormatClassNames.length != extraMetadataFormatNames.length!");
}
this.extraMetadataFormatNames =
(String[]) extraMetadataFormatNames.clone();
this.extraMetadataFormatClassNames =
(String[]) extraMetadataFormatClassNames.clone();
} else {
if (extraMetadataFormatClassNames != null) {
throw new IllegalArgumentException
("extraMetadataFormatNames == null && extraMetadataFormatClassNames != null!");
}
}
}
/**
* Returns <code>true if the standard metadata format is
* supported by <code>getMetadataFormat,
* <code>getAsTree, setFromTree, and
* <code>mergeTree.
*
* <p> The default implementation returns the value of the
* <code>standardFormatSupported instance variable.
*
* @return <code>true if the standard metadata format
* is supported.
*
* @see #getAsTree
* @see #setFromTree
* @see #mergeTree
* @see #getMetadataFormat
*/
public boolean isStandardMetadataFormatSupported() {
return standardFormatSupported;
}
/**
* Returns <code>true if this object does not support the
* <code>mergeTree, setFromTree, and
* <code>reset methods.
*
* @return true if this <code>IIOMetadata object cannot be
* modified.
*/
public abstract boolean isReadOnly();
/**
* Returns the name of the "native" metadata format for this
* plug-in, which typically allows for lossless encoding and
* transmission of the metadata stored in the format handled by
* this plug-in. If no such format is supported,
* <code>nullwill be returned.
*
* <p> The structure and contents of the "native" metadata format
* are defined by the plug-in that created this
* <code>IIOMetadata object. Plug-ins for simple formats
* will usually create a dummy node for the root, and then a
* series of child nodes representing individual tags, chunks, or
* keyword/value pairs. A plug-in may choose whether or not to
* document its native format.
*
* <p> The default implementation returns the value of the
* <code>nativeMetadataFormatName instance variable.
*
* @return the name of the native format, or <code>null.
*
* @see #getExtraMetadataFormatNames
* @see #getMetadataFormatNames
*/
public String getNativeMetadataFormatName() {
return nativeMetadataFormatName;
}
/**
* Returns an array of <code>Strings containing the names
* of additional metadata formats, other than the native and standard
* formats, recognized by this plug-in's
* <code>getAsTree, setFromTree, and
* <code>mergeTree methods. If there are no such additional
* formats, <code>null is returned.
*
* <p> The default implementation returns a clone of the
* <code>extraMetadataFormatNames instance variable.
*
* @return an array of <code>Strings with length at least
* 1, or <code>null.
*
* @see #getAsTree
* @see #setFromTree
* @see #mergeTree
* @see #getNativeMetadataFormatName
* @see #getMetadataFormatNames
*/
public String[] getExtraMetadataFormatNames() {
if (extraMetadataFormatNames == null) {
return null;
}
return (String[])extraMetadataFormatNames.clone();
}
/**
* Returns an array of <code>Strings containing the names
* of all metadata formats, including the native and standard
* formats, recognized by this plug-in's <code>getAsTree,
* <code>setFromTree, and mergeTree methods.
* If there are no such formats, <code>null is returned.
*
* <p> The default implementation calls
* <code>getNativeMetadataFormatName,
* <code>isStandardMetadataFormatSupported, and
* <code>getExtraMetadataFormatNames and returns the
* combined results.
*
* @return an array of <code>Strings.
*
* @see #getNativeMetadataFormatName
* @see #isStandardMetadataFormatSupported
* @see #getExtraMetadataFormatNames
*/
public String[] getMetadataFormatNames() {
String nativeName = getNativeMetadataFormatName();
String standardName = isStandardMetadataFormatSupported() ?
IIOMetadataFormatImpl.standardMetadataFormatName : null;
String[] extraNames = getExtraMetadataFormatNames();
int numFormats = 0;
if (nativeName != null) {
++numFormats;
}
if (standardName != null) {
++numFormats;
}
if (extraNames != null) {
numFormats += extraNames.length;
}
if (numFormats == 0) {
return null;
}
String[] formats = new String[numFormats];
int index = 0;
if (nativeName != null) {
formats[index++] = nativeName;
}
if (standardName != null) {
formats[index++] = standardName;
}
if (extraNames != null) {
for (int i = 0; i < extraNames.length; i++) {
formats[index++] = extraNames[i];
}
}
return formats;
}
/**
* Returns an <code>IIOMetadataFormat object describing the
* given metadata format, or <code>null if no description
* is available. The supplied name must be one of those returned
* by <code>getMetadataFormatNames (i.e., either the
* native format name, the standard format name, or one of those
* returned by <code>getExtraMetadataFormatNames).
*
* <p> The default implementation checks the name against the
* global standard metadata format name, and returns that format
* if it is supported. Otherwise, it checks against the native
* format names followed by any additional format names. If a
* match is found, it retrieves the name of the
* <code>IIOMetadataFormat class from
* <code>nativeMetadataFormatClassName or
* <code>extraMetadataFormatClassNames as appropriate, and
* constructs an instance of that class using its
* <code>getInstance method.
*
* @param formatName the desired metadata format.
*
* @return an <code>IIOMetadataFormat object.
*
* @exception IllegalArgumentException if <code>formatName
* is <code>null or is not one of the names recognized by
* the plug-in.
* @exception IllegalStateException if the class corresponding to
* the format name cannot be loaded.
*/
public IIOMetadataFormat getMetadataFormat(String formatName) {
if (formatName == null) {
throw new IllegalArgumentException("formatName == null!");
}
if (standardFormatSupported
&& formatName.equals
(IIOMetadataFormatImpl.standardMetadataFormatName)) {
return IIOMetadataFormatImpl.getStandardFormatInstance();
}
String formatClassName = null;
if (formatName.equals(nativeMetadataFormatName)) {
formatClassName = nativeMetadataFormatClassName;
} else if (extraMetadataFormatNames != null) {
for (int i = 0; i < extraMetadataFormatNames.length; i++) {
if (formatName.equals(extraMetadataFormatNames[i])) {
formatClassName = extraMetadataFormatClassNames[i];
break; // out of for
}
}
}
if (formatClassName == null) {
throw new IllegalArgumentException("Unsupported format name");
}
try {
Class cls = null;
final Object o = this;
// firstly we try to use classloader used for loading
// the IIOMetadata implemantation for this plugin.
ClassLoader loader = (ClassLoader)
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public Object run() {
return o.getClass().getClassLoader();
}
});
try {
cls = Class.forName(formatClassName, true,
loader);
} catch (ClassNotFoundException e) {
// we failed to load IIOMetadataFormat class by
// using IIOMetadata classloader.Next try is to
// use thread context classloader.
loader = (ClassLoader)
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public Object run() {
return Thread.currentThread().getContextClassLoader();
}
});
try {
cls = Class.forName(formatClassName, true,
loader);
} catch (ClassNotFoundException e1) {
// finally we try to use system classloader in case
// if we failed to load IIOMetadataFormat implementation
// class above.
cls = Class.forName(formatClassName, true,
ClassLoader.getSystemClassLoader());
}
}
Method meth = cls.getMethod("getInstance");
return (IIOMetadataFormat) meth.invoke(null);
} catch (Exception e) {
RuntimeException ex =
new IllegalStateException ("Can't obtain format");
ex.initCause(e);
throw ex;
}
}
/**
* Returns an XML DOM <code>Node object that represents the
* root of a tree of metadata contained within this object
* according to the conventions defined by a given metadata
* format.
*
* <p> The names of the available metadata formats may be queried
* using the <code>getMetadataFormatNames method.
*
* @param formatName the desired metadata format.
*
* @return an XML DOM <code>Node object forming the
* root of a tree.
*
* @exception IllegalArgumentException if <code>formatName
* is <code>null or is not one of the names returned by
* <code>getMetadataFormatNames.
*
* @see #getMetadataFormatNames
* @see #setFromTree
* @see #mergeTree
*/
public abstract Node getAsTree(String formatName);
/**
* Alters the internal state of this <code>IIOMetadata
* object from a tree of XML DOM <code>Nodes whose syntax
* is defined by the given metadata format. The previous state is
* altered only as necessary to accommodate the nodes that are
* present in the given tree. If the tree structure or contents
* are invalid, an <code>IIOInvalidTreeException will be
* thrown.
*
* <p> As the semantics of how a tree or subtree may be merged with
* another tree are completely format-specific, plug-in authors may
* implement this method in whatever manner is most appropriate for
* the format, including simply replacing all existing state with the
* contents of the given tree.
*
* @param formatName the desired metadata format.
* @param root an XML DOM <code>Node object forming the
* root of a tree.
*
* @exception IllegalStateException if this object is read-only.
* @exception IllegalArgumentException if <code>formatName
* is <code>null or is not one of the names returned by
* <code>getMetadataFormatNames.
* @exception IllegalArgumentException if <code>root is
* <code>null.
* @exception IIOInvalidTreeException if the tree cannot be parsed
* successfully using the rules of the given format.
*
* @see #getMetadataFormatNames
* @see #getAsTree
* @see #setFromTree
*/
public abstract void mergeTree(String formatName, Node root)
throws IIOInvalidTreeException;
/**
* Returns an <code>IIOMetadataNode representing the chroma
* information of the standard <code>javax_imageio_1.0
* metadata format, or <code>null if no such information is
* available. This method is intended to be called by the utility
* routine <code>getStandardTree.
*
* <p> The default implementation returns null.
*
* <p> Subclasses should override this method to produce an
* appropriate subtree if they wish to support the standard
* metadata format.
*
* @return an <code>IIOMetadataNode, or null.
*
* @see #getStandardTree
*/
protected IIOMetadataNode getStandardChromaNode() {
return null;
}
/**
* Returns an <code>IIOMetadataNode representing the
* compression information of the standard
* <code>javax_imageio_1.0 metadata format, or
* <code>null if no such information is available. This
* method is intended to be called by the utility routine
* <code>getStandardTree.
*
* <p> The default implementation returns null.
*
* <p> Subclasses should override this method to produce an
* appropriate subtree if they wish to support the standard
* metadata format.
*
* @return an <code>IIOMetadataNode, or null.
*
* @see #getStandardTree
*/
protected IIOMetadataNode getStandardCompressionNode() {
return null;
}
/**
* Returns an <code>IIOMetadataNode representing the data
* format information of the standard
* <code>javax_imageio_1.0 metadata format, or
* <code>null if no such information is available. This
* method is intended to be called by the utility routine
* <code>getStandardTree.
*
* <p> The default implementation returns null.
*
* <p> Subclasses should override this method to produce an
* appropriate subtree if they wish to support the standard
* metadata format.
*
* @return an <code>IIOMetadataNode, or null.
*
* @see #getStandardTree
*/
protected IIOMetadataNode getStandardDataNode() {
return null;
}
/**
* Returns an <code>IIOMetadataNode representing the
* dimension information of the standard
* <code>javax_imageio_1.0 metadata format, or
* <code>null if no such information is available. This
* method is intended to be called by the utility routine
* <code>getStandardTree.
*
* <p> The default implementation returns null.
*
* <p> Subclasses should override this method to produce an
* appropriate subtree if they wish to support the standard
* metadata format.
*
* @return an <code>IIOMetadataNode, or null.
*
* @see #getStandardTree
*/
protected IIOMetadataNode getStandardDimensionNode() {
return null;
}
/**
* Returns an <code>IIOMetadataNode representing the document
* information of the standard <code>javax_imageio_1.0
* metadata format, or <code>null if no such information is
* available. This method is intended to be called by the utility
* routine <code>getStandardTree.
*
* <p> The default implementation returns null.
*
* <p> Subclasses should override this method to produce an
* appropriate subtree if they wish to support the standard
* metadata format.
*
* @return an <code>IIOMetadataNode, or null.
*
* @see #getStandardTree
*/
protected IIOMetadataNode getStandardDocumentNode() {
return null;
}
/**
* Returns an <code>IIOMetadataNode representing the textual
* information of the standard <code>javax_imageio_1.0
* metadata format, or <code>null if no such information is
* available. This method is intended to be called by the utility
* routine <code>getStandardTree.
*
* <p> The default implementation returns null.
*
* <p> Subclasses should override this method to produce an
* appropriate subtree if they wish to support the standard
* metadata format.
*
* @return an <code>IIOMetadataNode, or null.
*
* @see #getStandardTree
*/
protected IIOMetadataNode getStandardTextNode() {
return null;
}
/**
* Returns an <code>IIOMetadataNode representing the tiling
* information of the standard <code>javax_imageio_1.0
* metadata format, or <code>null if no such information is
* available. This method is intended to be called by the utility
* routine <code>getStandardTree.
*
* <p> The default implementation returns null.
*
* <p> Subclasses should override this method to produce an
* appropriate subtree if they wish to support the standard
* metadata format.
*
* @return an <code>IIOMetadataNode, or null.
*
* @see #getStandardTree
*/
protected IIOMetadataNode getStandardTileNode() {
return null;
}
/**
* Returns an <code>IIOMetadataNode representing the
* transparency information of the standard
* <code>javax_imageio_1.0 metadata format, or
* <code>null if no such information is available. This
* method is intended to be called by the utility routine
* <code>getStandardTree.
*
* <p> The default implementation returns null.
*
* <p> Subclasses should override this method to produce an
* appropriate subtree if they wish to support the standard
* metadata format.
*
* @return an <code>IIOMetadataNode, or null.
*/
protected IIOMetadataNode getStandardTransparencyNode() {
return null;
}
/**
* Appends a new node to an existing node, if the new node is
* non-<code>null.
*/
private void append(IIOMetadataNode root, IIOMetadataNode node) {
if (node != null) {
root.appendChild(node);
}
}
/**
* A utility method to return a tree of
* <code>IIOMetadataNodes representing the metadata
* contained within this object according to the conventions of
* the standard <code>javax_imageio_1.0 metadata format.
*
* <p> This method calls the various getStandard*Node
* methods to supply each of the subtrees rooted at the children
* of the root node. If any of those methods returns
* <code>null, the corresponding subtree will be omitted.
* If all of them return <code>null, a tree consisting of a
* single root node will be returned.
*
* @return an <code>IIOMetadataNode representing the root
* of a metadata tree in the <code>javax_imageio_1.0
* format.
*
* @see #getStandardChromaNode
* @see #getStandardCompressionNode
* @see #getStandardDataNode
* @see #getStandardDimensionNode
* @see #getStandardDocumentNode
* @see #getStandardTextNode
* @see #getStandardTileNode
* @see #getStandardTransparencyNode
*/
protected final IIOMetadataNode getStandardTree() {
IIOMetadataNode root = new IIOMetadataNode
(IIOMetadataFormatImpl.standardMetadataFormatName);
append(root, getStandardChromaNode());
append(root, getStandardCompressionNode());
append(root, getStandardDataNode());
append(root, getStandardDimensionNode());
append(root, getStandardDocumentNode());
append(root, getStandardTextNode());
append(root, getStandardTileNode());
append(root, getStandardTransparencyNode());
return root;
}
/**
* Sets the internal state of this <code>IIOMetadata object
* from a tree of XML DOM <code>Nodes whose syntax is
* defined by the given metadata format. The previous state is
* discarded. If the tree's structure or contents are invalid, an
* <code>IIOInvalidTreeException will be thrown.
*
* <p> The default implementation calls reset
* followed by <code>mergeTree(formatName, root).
*
* @param formatName the desired metadata format.
* @param root an XML DOM <code>Node object forming the
* root of a tree.
*
* @exception IllegalStateException if this object is read-only.
* @exception IllegalArgumentException if <code>formatName
* is <code>null or is not one of the names returned by
* <code>getMetadataFormatNames.
* @exception IllegalArgumentException if <code>root is
* <code>null.
* @exception IIOInvalidTreeException if the tree cannot be parsed
* successfully using the rules of the given format.
*
* @see #getMetadataFormatNames
* @see #getAsTree
* @see #mergeTree
*/
public void setFromTree(String formatName, Node root)
throws IIOInvalidTreeException {
reset();
mergeTree(formatName, root);
}
/**
* Resets all the data stored in this object to default values,
* usually to the state this object was in immediately after
* construction, though the precise semantics are plug-in specific.
* Note that there are many possible default values, depending on
* how the object was created.
*
* @exception IllegalStateException if this object is read-only.
*
* @see javax.imageio.ImageReader#getStreamMetadata
* @see javax.imageio.ImageReader#getImageMetadata
* @see javax.imageio.ImageWriter#getDefaultStreamMetadata
* @see javax.imageio.ImageWriter#getDefaultImageMetadata
*/
public abstract void reset();
/**
* Sets the <code>IIOMetadataController to be used
* to provide settings for this <code>IIOMetadata
* object when the <code>activateController method
* is called, overriding any default controller. If the
* argument is <code>null, no controller will be
* used, including any default. To restore the default, use
* <code>setController(getDefaultController()).
*
* <p> The default implementation sets the controller
* instance variable to the supplied value.
*
* @param controller An appropriate
* <code>IIOMetadataController, or null.
*
* @see IIOMetadataController
* @see #getController
* @see #getDefaultController
* @see #hasController
* @see #activateController()
*/
public void setController(IIOMetadataController controller) {
this.controller = controller;
}
/**
* Returns whatever <code>IIOMetadataController is currently
* installed. This could be the default if there is one,
* <code>null, or the argument of the most recent call
* to <code>setController.
*
* <p> The default implementation returns the value of the
* <code>controller instance variable.
*
* @return the currently installed
* <code>IIOMetadataController, or null.
*
* @see IIOMetadataController
* @see #setController
* @see #getDefaultController
* @see #hasController
* @see #activateController()
*/
public IIOMetadataController getController() {
return controller;
}
/**
* Returns the default <code>IIOMetadataController, if there
* is one, regardless of the currently installed controller. If
* there is no default controller, returns <code>null.
*
* <p> The default implementation returns the value of the
* <code>defaultController instance variable.
*
* @return the default <code>IIOMetadataController, or
* <code>null.
*
* @see IIOMetadataController
* @see #setController(IIOMetadataController)
* @see #getController
* @see #hasController
* @see #activateController()
*/
public IIOMetadataController getDefaultController() {
return defaultController;
}
/**
* Returns <code>true if there is a controller installed
* for this <code>IIOMetadata object.
*
* <p> The default implementation returns true if the
* <code>getController method returns a
* non-<code>null value.
*
* @return <code>true if a controller is installed.
*
* @see IIOMetadataController
* @see #setController(IIOMetadataController)
* @see #getController
* @see #getDefaultController
* @see #activateController()
*/
public boolean hasController() {
return (getController() != null);
}
/**
* Activates the installed <code>IIOMetadataController for
* this <code>IIOMetadata object and returns the resulting
* value. When this method returns <code>true, all values for this
* <code>IIOMetadata object will be ready for the next write
* operation. If <code>false is
* returned, no settings in this object will have been disturbed
* (<i>i.e., the user canceled the operation).
*
* <p> Ordinarily, the controller will be a GUI providing a user
* interface for a subclass of <code>IIOMetadata for a
* particular plug-in. Controllers need not be GUIs, however.
*
* <p> The default implementation calls getController
* and the calls <code>activate on the returned object if
* <code>hasController returns true.
*
* @return <code>true if the controller completed normally.
*
* @exception IllegalStateException if there is no controller
* currently installed.
*
* @see IIOMetadataController
* @see #setController(IIOMetadataController)
* @see #getController
* @see #getDefaultController
* @see #hasController
*/
public boolean activateController() {
if (!hasController()) {
throw new IllegalStateException("hasController() == false!");
}
return getController().activate(this);
}
}
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